Sheet conveying apparatus, and image forming apparatus

ABSTRACT

An upper conveyance guide is provided at an apparatus main body. A guide surface of a lower conveyance guide is provided facing a guide surface of the upper conveyance guide, and can be drawn out in the direction intersecting the sheet conveyance direction with respect to the apparatus main body. A cleaning unit is provided on the backside in the drawing-out direction of the lower conveyance guide, moves together with the lower conveyance guide when the lower conveyance guide is drawn out from the apparatus main body, and cleans the guide surface of the upper conveyance guide.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet conveying apparatus having aconveyance guide, and to an image forming apparatus including the sheetconveying apparatus, e.g., a copying machine, a printer, a facsimile, ora multifunction peripheral of these apparatuses. More particularly, thepresent invention relates to cleaning of the conveyance guide which isequipped in the apparatus main body.

2. Description of the Related Art

A conventional electro-photographic image forming apparatus, such as acopying machine, a printer, a facsimile, or a multifunction peripheralof these apparatuses, includes a sheet conveying apparatus configured toconvey a sheet, and an image forming unit configured to form a tonerimage on the sheet which has been conveyed by the sheet conveyingapparatus. In general, the sheet conveying apparatus has a conveyanceguide for guiding a sheet to be conveyed, and is configured to guide thesheet between the conveyance guides.

In recent years, a print on-demand (POD) market has required highproductivity, increased function, and high durability for an imageforming apparatus used in the POD market. Since the image formingapparatus deals with many media, the image forming apparatus may conveya sheet containing much paper dusts. Further, in such a highly durableimage forming apparatus, a large number of sheets passes through theapparatus in one period of service maintenance. Therefore, in the imageforming apparatus, the paper dusts coming from the sheets couldaccumulate on the conveyance guide in large quantity.

In such an image forming apparatus, since the paper dusts accumulates onthe conveyance guide as use time increases, the accumulated paper dustscould generate conveyance faults of a sheet or image defects. Thus, inorder to prevent these problems, the conveyance guide is configured tobe a drawable conveyance unit, and an operator cleans the conveyanceguide by drawing out the conveyance unit from an apparatus main body ata time of service maintenance.

Japanese Patent Application Laid-Open No. 2000-118760 discusses atechnique by which a user can easily clean a part where paper dusts havea tendency to accumulate. In this technique, an apparatus main bodyincludes a cleaning unit which is in contact with a conveyance guideserving as a sheet control member. By drawing out the conveyance guidein the direction intersecting the sheet conveyance direction, a user canclean paper dusts and dusts accumulating on the conveyance guide.

In recent years, positioning of an image leading edge and a sheet(leading edge registration) with higher accuracy has become necessary toimprove an image quality. Thus, conveyance units on the upstream side ofan image bearing member such as a photosensitive drum or an intermediatetransfer belt, adopt following configuration in many cases. When a pairof upper and lower conveyance guides is configured to be drawn out tothe outside as a unit, an attachment position deviates at a time ofattaching and conveyance accuracy decreases. Thus, only a lowerconveyance guide of the conveyance unit can be drawn out. In addition,according to this configuration of the conveyance unit, an operator canbe prevented from accidentally touching and damaging the image bearingmembers such as a photosensitive drum and an intermediate transfer beltduring a cleaning operation.

When only one of a pair of the conveyance guides is configured to bedrawn out, an operator can easily draw out and clean the conveyanceguide. However, an operator should put his or her hand into an apparatusmain body and cleans the conveyance guide remaining in the apparatusmain body. Thus, the operator can not fully clean the conveyance guideremaining in the apparatus main body. Therefore, an apparatus havinggood operability which can be more accurately cleaned is required.

SUMMARY OF THE INVENTION

The present invention is directed to a sheet conveying apparatus and aimage forming apparatus which are capable of efficiently cleaning aconveyance guide provided in an apparatus main body.

According to an aspect of the present invention, a sheet conveyingapparatus configured to convey a sheet along a sheet conveyance pathprovided in an apparatus main body includes a first conveyance guide, asecond conveyance guide, and a cleaning unit. The first conveyance guidehas a first guide surface for guiding a sheet. The second conveyanceguide has a second guide surface arranged facing the first guide surfaceof the first conveyance guide. The second conveyance guide serves as thesheet conveyance path together with the first conveyance guide, and canbe drawn out in a direction intersecting a sheet conveyance directionwith respect to the apparatus main body. The cleaning unit is providedon a back side in the drawing-out direction of the second conveyanceguide. The cleaning unit moves together with the second conveyance guidewhen the second conveyance guide is drawn out from the apparatus mainbody, and cleans the first guide surface of the first conveyance guide.The cleaning unit includes a cleaning member being in contact with thefirst guide surface of the first conveyance guide, and a pushing memberto push the cleaning member toward the first guide surface side.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 schematically illustrates a printer as one example of an imageforming apparatus according to the first exemplary embodiment of thepresent invention.

FIG. 2 is a perspective view for schematically illustrating a state thata conveyance unit of a printer is drawn out from a printer main body.

FIG. 3 is an enlarged view for illustrating a transfer unit and itsneighborhood illustrated in FIG. 1.

FIG. 4 is a side view for illustrating a cleaning unit in a state ofdrawing out a conveyance unit from a printer main body.

FIGS. 5A, 5B, 5C, 5D, and 5E illustrate a cleaning unit cleaning a guidesurface of an upper conveyance guide in conjunction with a drawing-outoperation and an attaching operation for a lower conveyance guide.

FIGS. 6A, 6B, and 6C illustrate how a gap between a pair of conveyanceguides changes by the drawing-out operation of the conveyance unit.

FIG. 7 is a bottom view for illustrating an upper conveyance guide and acleaning unit facing the upper conveyance guide.

FIG. 8 illustrates an attachment structure of a cleaning unit.

FIG. 9 illustrates a configuration of a cleaning unit in a secondaryexemplary embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

FIG. 1 schematically illustrates a printer as one example of an imageforming apparatus according to the first exemplary embodiment of thepresent invention.

In FIG. 1, a printer 1 is an image forming apparatus, and a printer 110is a main body of the image forming apparatus.

The printer 1 includes a document feeding apparatus 120 arranged on theupper side of the printer main body 110, and an image reading unit 130which reads a document laid on an original stacking stand (notillustrated). Further, the printer 1 includes a sheet conveyingapparatus 140 configured to convey a sheet S, an image forming unit 100configured to forma toner image on the sheet S conveyed by the sheetconveying apparatus 140, and a fixing unit 300 configured to fix thetoner image formed by the image forming unit 100 on the sheet S.

The sheet conveying apparatus 140 includes a sheet feeding unit 141configured to feed the sheet S, a sheet conveyance path 142 forconveying the sheet S, and a skew correction mechanism 148 which is askew correction unit configured to perform skew correction or timingcorrection of the sheet S. The sheet conveying apparatus 140 includes aplurality of conveyance roller pairs 151 to 156 provided at the sheetconveyance path 142. The sheet conveying apparatus 140 includes adischarge roller pair 180 provided at a path 160 of the sheet conveyancepath 142. The discharge roller pair 180 discharges the sheet S carryingthe image fixed by the fixing unit 300, from the printer main body 110.The sheet conveying apparatus 140 conveys a sheet along the sheetconveyance path 142 by these conveyance roller pairs (conveyance means).

The skew correction mechanism 148 is an active registration type forcorrecting skew of the sheet S while conveying the sheet S. The skewcorrection mechanism 148 includes two skew correction roller pairs 148 aand 148 a arranged at each side in the width direction intersecting thesheet conveyance direction, and includes two shift roller pairs 148 band 148 b arranged at each side in the width direction. FIG. 1illustrates only each one of these roller pairs and shift roller pairs.The skew correction roller pairs 148 a and 148 a are independentlydriven and rotated, and can rotate at different conveying speeds fromeach other. The shift roller pairs 148 b and 148 b can slide in widthdirection. The conveying speed of the skew correction roller pairs 148 aand 148 a is set according to a skew amount of the sheet S. Accordingly,the skew of the sheet S is corrected while it is conveyed by each of theskew correction roller pairs 148 a and 148 a. Further, the position ofthe sheet S is corrected in the width direction by the shift rollerpairs 148 b and 148 b.

The image forming unit 100 is arranged on the downstream side in thesheet conveyance direction of the skew correction mechanism 148. Theimage forming unit 100 includes a photosensitive drum 102, a transferunit 104 configured to transfer a toner image on the sheet S, and anexposure unit 101, and further includes a charging device and adevelopment device which are not illustrated.

The transfer unit 104 includes an intermediate transfer belt 105stretched, conveyed, and driven by rollers such as a drive roller 104 a,a tension roller 104 b, and a transfer counter roller 103. Further, thetransfer unit 104 includes a transfer roller 106 pressure-contacting theintermediate transfer belt 105 pressured by the transfer counter roller103. A transfer nip portion is formed by pressure-contacting thetransfer roller 106 with the intermediate transfer belt 105.

The sheet feeding unit 141 includes a cassette 145 which is a sheetaccommodating unit for accommodating a plurality of the sheets S, and apickup roller 146 for feeding the sheets S accommodated in the cassette145. The cassette 145 can selectively accommodate various kinds of thesheets S.

In the printer 1 having the aforementioned configuration, when a controldevice (not illustrated) provided at the printer main body 110 outputsan image reading signal to the image reading unit 130, the image readingunit 130 reads an image.

Then, the charging device (not illustrated) uniformly charges thesurface of the photosensitive drum 102. Next, the exposure unit 101forms a latent image on the surface of the photosensitive drum 102 byexposing it with light. Then, the development device performs tonerdevelopment on the electrostatic latent image formed on thephotosensitive drum 102 and forms a toner image on the photosensitivedrum 102. The toner image is transferred onto the intermediate transferbelt 105.

A cleaner (not illustrated) for cleaning a toner and paper dustscontacts the surface of the intermediate transfer belt 105 and thesurface of the photosensitive drum 102 to clean each surface.

When the control device (not illustrated) outputs a paper feed signal tothe sheet feeding unit 141, the pickup roller 146 feeds the sheet S oneby one from the cassette 145 in which sheets S having a designated sizeare accommodated. The conveyance roller pairs 151 to 156 convey the fedsheets S to the skew correction mechanism 148, and the skew correctionmechanism 148 corrects the skew.

After correcting the skew, the sheet S is conveyed to the transfer nipportion formed by the intermediate transfer belt 105 and the transferroller 106.

The sheet S onto which the intermediate transfer belt 105 and thetransfer roller 106 transfer the toner image is conveyed to the fixingunit 300 by a conveyance belt 107. In the fixing unit 300, rollers 300 aand 300 b which face each other heats and presses the sheet S, and fusesand fixes a toner on the sheet S.

The sheet S on which the image is fixed passes the path 160, anddischarged to a sheet post-processing apparatus (not illustrated) by thedischarge roller pair 180.

In addition, when an image is formed on two-sides of the sheet S, thesheet S is conveyed to a reversing path 170 by switching of a changeovermember (not illustrated). When the sheet S is conveyed to the reversingpath 170, the sheet s exchanges the front end and the back end byperforming a switch-back operation, and is conveyed to a re-conveyancepath 168.

Then, the sheet S enters the upstream side of the conveyance roller pair154 while coinciding the timing of the sheet S with the timing of asheet S of a succeeding job conveyed from the sheet feeding unit 141,and is fed to the image forming unit 100 through the conveyance rollers154 to 156 and the skew correction mechanism 148. Since the imageforming process of the sheet surface this time is similar to that in thefirst surface of the sheet, the description is omitted.

A pair of conveyance guides 202 and 203 which configure a part of thesheet conveyance path 142 is provided on the upstream side in the sheetconveyance direction of the image forming unit 100 and between the skewcorrection mechanism 148 and the transfer roller 106 (a transfer nipportion) of the image forming unit 100. The conveyance guide 202 (whichwill be hereinafter referred to as an upper conveyance guide) which is afirst conveyance guide is provided fixed on the printer main body 110.The upper conveyance guide 202 has a guide surface 202 g which is afirst guide surface.

The conveyance guide 203 (which will be referred to as a lowerconveyance guide) which is a second conveyance guide has a guide surface203 g which is a second guide surface. The guide surface 203 g isarranged facing the guide surface 202 g of the upper conveyance guide202. The lower conveyance guide 203 is arranged on the lower side of theupper conveyance guide 202 and guides a sheet with the guide surface 202g of the lower surface of the upper conveyance guide 202 and the guidesurface 203 g of the upper surface of the lower conveyance guide 203.

In the first exemplary embodiment, a conveyance unit 200 is configuredby integrating the skew correction mechanism 148, the lower conveyanceguide 203, the transfer roller 106, the conveyance belt 107, the fixingunit 300, the re-conveyance path 168, and the conveyance roller pairsprovided at the re-conveyance path 168. The conveyance unit 200 issupported by a pair of rail mechanisms 201 and 201 and can be drawn outin the direction intersecting the sheet conveyance direction withrespect to the printer main body 110.

The pair of rail mechanisms 201 and 201 is provided horizontally. Thelower conveyance guide 203 is approximate-horizontally drawn out fromthe printer main body 110 while the guide surface 202 g of the upperconveyance guide 202 is approximately parallel with the guide surface203 g of the lower conveyance guide 203.

FIG. 2 is a perspective view for schematically illustrating theconveyance unit 200 of the printer 1 drawn out from the printer mainbody 110.

The conveyance unit 200 has an operation lever 200 a which can lock orcancel the locking with respect to the printer main body 110. Anoperator operates the operation lever 200 a to cancel the locking byrotating, and the conveyance unit 200 can be drawn out in the direction(the direction illustrated with an arrow A in FIG. 2) intersecting thesheet conveyance direction along the rail mechanism 201. The conveyanceunit 200 is drawn out by sliding toward the front side of the printermain body 110 (toward the position F side in FIG. 2).

Further, the drawn conveyance unit 200 slides in the direction oppositeto the arrow A direction, and is attached to the back side of theprinter main body 110 (the position R side in FIG. 2). In addition, astopper (not illustrated) is provided to prevent the conveyance unit 200from coming off and falling from the rail mechanism 201 when theconveyance unit 200 is drawn out.

The lower conveyance guide 203 is arranged on the upper surface of amain body of the conveyance unit 200, and is exposed to an external whenthe conveyance unit 200 is drawn out from the printer main body 110.When the conveyance unit 200 is drawn out, the lower conveyance guide203 is drawn out in the arrow A direction from the printer main body110. However, the upper conveyance guide 202 (FIG. 1) is not drawn outsince the upper conveyance guide 202 is fixed to the printer main body110. The upper conveyance guide 202 and the lower conveyance guide 203are formed longer than the length of a paper passing area in the widthdirection intersecting with the sheet conveyance direction. The paperpassing area has a maximum size of a sheet to be conveyed, and covers adeviation range of the sheet in the width direction (horizontalregistration).

Here, the paper dusts adhere to the upper conveyance 202 (FIG. 1) when asheet to be conveyed is rubbed.

A cleaning unit 205 configured to clean the upper conveyance guide 202is provided at a position on the back side (the position R side in FIG.2) in the drawing-out direction of the lower conveyance guide 203. Thecleaning unit 205 is arranged outside the paper passing area.

The cleaning unit 205 is fixed on the lower conveyance guide 203, andmoves together with the lower conveyance guide 203 when the lowerconveyance guide 203 is drawn out from the printer main body 110.Accordingly, the cleaning unit 205 cleans a approximately entire area inthe width direction intersecting with the sheet conveyance direction ofthe upper conveyance guide 202. Therefore, the upper conveyance guide202 can be efficiently cleaned by the cleaning unit 205.

A configuration of the upper conveyance guide 202 which is an object tobe cleaned will be described in detail below. FIG. 3 is an enlarged viewof the transfer unit 104 illustrated in FIG. 1 and its neighborhood.

The upper conveyance guide 202 includes a guide base body 202A, and twosheet control members 204 and 204A fixed to the guide base body 202A.The guide base body 202A is made of a metal or a hard material such as ahard resin, and is fixed to the printer main body 110. The guide basebody 202A and the sheet control members 204 and 204A are formed suchthat an entire length in the width direction is longer than the lengthin the width direction of the paper passing area.

The sheet control members 204 and 204A are formed in a thin sheet state,and is made of a flexible material (e.g., a resin). The sheet controlmembers 204 and 204A extend on the downstream side in the sheetconveyance direction, and is projecting toward a conveyance space towhich a sheet is conveyed from the guide base body 202A. When the sheetis conveyed, the sheet control members 204 and 204A contact the surface(the upper surface) of the sheet, and control an orientation of thesheet. Accordingly, the skew and the position of a leading edge of thesheet in the width direction are corrected by the skew correctionmechanism 148, and the sheet is well guided to the transfer unit 104 ofthe image forming unit 100, and a positional deviation of an imageformed on the sheet decreases. Thus, the positional accuracy of an imageformed on the sheet is improved.

The sheet control members 204 and 204A have flexibility. When the sheetis thin, the sheet control members 204 and 204A hardly bend and is in astate as illustrated in FIG. 3. However, when the sheet is thick, thesheet control members 204 and 204A bend due to rigidity of the sheet, sothat the conveyance resistance of the sheet decreases.

The sheet control member 204 is arranged to be in contact with the guidesurface 203 g of the lower conveyance guide 203 arranged downward, andis always in slidable contact with the surface (the upper surface) ofthe sheet conveyed. Therefore, paper dusts easily adhere to the guidesurface of the sheet control member 204. Further, the paper dustsadhering to the sheet control member 204 easily scatter to the guidesurface of the guide base body 202A and the guide surface of the sheetcontrol member 204A. In addition, the guide surface of the guide basebody 202A, the guide surface of the sheet control member 204, and theguide surface of the sheet control member 204A are facing the guidesurface 203 g of the lower conveyance guide 203, and constitute theguide surface 202 g of the upper conveyance guide 202.

In the first exemplary embodiment, the cleaning unit 205 is arranged onthe back side in the direction parallel with the drawing-out direction,on the lower conveyance guide 203. Thus, together with a drawing-outoperation of the conveyance unit 200 (the lower conveyance guide 203),the cleaning unit 205 cleans the guide surfaces of the sheet controlmembers 204 and 204A, and the guide base body 202A.

FIG. 4 is a side view for illustrating the cleaning unit 205 when theconveyance unit 200 is drawn out from the printer main body 110.

The cleaning unit 205 includes a cleaning member 205 a in contact withthe guide surface 202 g of the upper conveyance guide 202, and anelastic member 205 b as a pushing member for pushing the cleaning member205 a toward the first guide surface of the upper conveyance guide 202.The cleaning member 205 a is elastic and deformable, and formed bybundling elastically deformable wire-shaped members made of a syntheticresin, and is configured to absorb foreign matters such as paper dusts.

The cleaning member 205 a includes an elastic member 205 b fixed on theback surface with an adhesive. The elastic member 205 b is made of afoamable material, which is extensible and contractible in the arrow Edirection vertical to the guide surface 202 g of the upper conveyanceguide 202. Accordingly, since the cleaning unit 205 can be produced byan easy operation of attaching the elastic member 205 b made of afoamable material to the cleaning member 205 a, manufacturing cost canbe reduced.

Further, when the lower conveyance guide 203 is attached to the printermain body 110, the elastic member 205 b is deformed under pressure, andrestoration force (urging force) of the compressed and deformed elasticmaterial 205 b presses the cleaning member 205 a to the guide surface202 g of the upper conveyance guide 202. By forming a double-layer ofthe cleaning member 205 a and the elastic member 205 b, the elasticmember 205 b causes the cleaning member 205 a to accurately contact theguide surface 202 g of the upper conveyance guide 202, and a favourablecleaning ability free from cleaning failure can be obtained.

When the lower conveyance guide 203 is drawn out from the printer mainbody 110, the cleaning unit 205 is not in contact with the upperconveyance guide 202 as illustrated in FIG. 4, so that the compressedelastic member 205 b returns to its original state. The elastic member205 b in a non-compressed state (an unloaded state) is formed projectingabove the guide surface 202 g of the upper conveyance guide 202.Further, when the lower conveyance guide 203 is attached to the printermain body 110, a protection sheet 206 which is a flexible member forprotecting the side surface of the elastic member 205 b is facing theside surface of the lower conveyance guide 203 on the back side in thedrawing-out direction in the elastic member 205 b.

FIG. 5 illustrates the cleaning unit 205 cleaning the guide surface 202g of the upper conveyance guide 202, together with the drawing-outoperation and attaching operation of the lower conveyance guide 203.FIG. 5A illustrates a state in the middle of drawing-out the lowerconveyance guide 203. FIG. 5B illustrates a state that the lowerconveyance guide 203 is in the middle of drawing-out and a part of thecleaning unit 205 is separated from the upper conveyance guide 202. FIG.5C illustrates a state that the lower conveyance guide 203 is drawn out.FIG. 5D illustrates a part of the cleaning unit 205 pressured to contactwith the upper conveyance guide 202 when the lower conveyance guide 203is attached. FIG. 5E illustrates the lower conveyance guide 203 in themiddle of attaching.

The elastic member 205 b is deformed by pressure to make the cleaningmember 205 a contact the guide surface 202 g of the upper conveyanceguide 202 under pressure. In this state, as illustrated in FIGS. 5A and5B, when the lower conveyance guide 203 is drawn out in the drawing-outdirection illustrated with the arrow A, the cleaning unit 205 removespaper dusts adhering to the guide surface 202 g of the upper conveyanceguide 202.

Accordingly, by arranging the cleaning unit 205 on the back side in thedrawing-out direction of the lower conveyance guide 203 indicated by thearrow A, it becomes possible to clean the approximately entire guidesurface 202 g in the width direction of the upper conveyance guide 202,together with the drawing-out operation of the conveyance unit 200.

Particularly, since the sheet control member 204 (FIG. 3) of the upperconveyance guide 202 certainly contacts the a conveyed sheet, paperdusts easily accumulate on the leading edge or the guide surface of thesheet control member 204.

In the first exemplary embodiment, since the sheet control member 204 iscleaned by the cleaning unit 205, paper dusts can be prevented fromfalling onto a sheet due to vibration induced by momentary bend of thesheet control member 204.

It is necessary to clean at least the sheet control member 204. However,in the first exemplary embodiment, the length in the sheet conveyancedirection of the cleaning unit 205 is set such that not only the sheetcontrol member 204 but also the sheet control member 204A and the guidebase body 202A can be cleaned. In other words, since the entire lengthin the sheet conveyance direction of the cleaning unit 205 is set to belonger than the entire length in the sheet conveyance directionincluding the guide base body 202A and the sheet control members 204 and204A, the cleaning unit 205 can sufficiently clean the guide surface 202g of the upper conveyance guide 202 without cleaning failure.Accordingly, paper dusts can be more efficiently prevented from fallingonto the sheet.

Therefore, image defects such as white spots can be prevented. The whitespots occur in an image on a sheet because a toner image is nottransferred onto a portion on which paper dusts fall. Particularly, inthe first exemplary embodiment, the image is formed on the upper surfaceof a sheet, so that image defects can be reduced more effectively bycleaning the upper conveyance unit 202 facing the upper surface of thesheet.

Even if periodical service maintenance is not performed for a user, theuser can unintentionally clean the upper conveyance guide 202 when theuser draws out the conveyance unit 200, for example, to carry out ajamming treatment when a sheet is jammed. The unintentional cleaning bya user is particularly effective for a high durable image formingapparatus in which a large number of sheets passes until time of servicemaintenance.

Since the cleaning unit 205 cleans the upper conveyance guide 202,cleaning effects without individual variations can be stably acquired.Further, since an operator does not need to put his or her hands intothe printer main body 110 to perform a cleaning operation, the operatordoes not damage the intermediate transfer belt 105. Further, theoperator does not access the inside of the printer main body 110 toclean the upper conveyance guide 202, and can thus efficiently clean theupper conveyance guide 202 with the cleaning unit 205.

When the lower conveyance guide 203 is drawn out from the printer mainbody 110 as illustrated in FIG. 5C, paper dusts SW scraped out by thecleaning unit 205 accumulates on the lower conveyance guide 203.However, since the lower conveyance guide 203 is drawn out externallyfrom the printer main body 110, an operator such as a user or aserviceman can easily clean the lower conveyance guide 203 when it isnecessary. Further, as the accumulating paper dusts SW are outside of aconveyance area, the paper dusts SW can be prevented from adhering to asheet conveyed.

As illustrated in FIG. 5D, when the lower conveyance guide 203 moves inthe attaching direction illustrated with the arrow B in the printer mainbody 110 direction, the protection sheet 206 comes to be in contact withan end of the upper conveyance guide 202. Thus, the end of the upperconveyance guide 202 does not hit the side of the elastic member 205 b.Therefore, since the protection sheet 206 protects the elastic member205 b, the elastic member 205 b can be prevented from damage. Then, theprotection sheet 206 is pressed by the end of the upper conveyance guide202 and bends while protecting the elastic member 205 b. A part of theelastic member 205 b is compressed and deformed by pressing of the endof the upper conveyance guide 202 through the protection sheet 206. Thecleaning member 205 a deforms while bending the bristles, andpressure-contacts the upper conveyance guide 202.

The protection sheet 206 protects the elastic member 205 b even when theupper conveyance guide 202 on the printer main body side is detached ata time of service maintenance. Thus, even when the upper conveyanceguide 202 comes to be in contact with the elastic member 205 b, theelastic member 205 can be prevented from damage.

The lower conveyance guide 203 may be detached from a main body of theconveyance unit 200 at a time of service maintenance. When the lowerconveyance guide 203 is attached to the main body of the conveyance unit200 again, the lower conveyance guide 203 may be attached by mistakerunning on other members. In this state, if the protection sheet 206 isnot provided, the elastic member 205 b could come to be in contact withthe other members not illustrated when the conveyance unit 200 isattached to the printer main body 110. By contrast, in the firstexemplary embodiment, since the protection sheet 206 protects theelastic member 205 b, the elastic member 205 b can be prevented fromcontacting the other members and from damage.

As illustrated in FIG. 5E, when the lower conveyance guide 203 is in themiddle of attaching to the printer main body 110, the entire elasticmember 205 b is compressed and deformed, and the cleaning member 205 acomes to be in slidable contact with the upper conveyance guide 202.

The conveyance unit 200 (illustrated in FIGS. 1 and 2) is a heavy weightsubstance. Thus, as the conveyance unit 200 is drawn out in thedrawing-out direction along the rail mechanism 201, the rail mechanism201 bends by the heavy weight of the conveyance unit 200, and theconveyance unit 200 goes downward in the gravity direction (lowerdirection). In the other words, even when an operator tries to draw theconveyance unit 200 horizontally in the direction intersecting the sheetconveyance direction from the printer main body 110, the conveyance unit200 declines in the gravity direction, and a gap between a pair of theconveyance guides 202 and 203 changes.

FIG. 6 illustrates pairs of gaps g1, g2, and g3 between the conveyanceguides 202 and 203, which change according to operations for drawing outthe conveyance unit 200. FIG. 6A illustrates the conveyance unit 200attached to the printer main body 110. FIG. 6B illustrates theconveyance unit 200 in the middle of drawing out from the printer mainbody 110. FIG. 6C illustrates the conveyance unit 200 drawn out from theprinter main body 110.

As illustrated in FIG. 6A, when the conveyance unit 200 is attached tothe printer main body 110, since the weight of the conveyance unit 200is uniformly applied on the rail mechanism 201, the bending amount ofthe rail mechanism 201 is the minimum, and the gap g1 between guides isthe minimum.

On the other hand, as illustrated in FIG. 6C, when the conveyance unit200 is drawn out from the printer main body 110, the weight of theconveyance unit 200 is applied concentrating on the end of the railmechanism 201. Thus, the bending amount of the rail mechanism 201 is themaximum, and the gap g3 between guides is the maximum.

As illustrated in FIG. 6B, when the conveyance unit 200 is in the middleof drawing out from the printer main body 100, the bending amount of therail mechanism 201 is a middle value between the maximum and minimum,and the gap 2 between guides is also the middle value between themaximum and minimum. In other words, the relation of the gap g1, the gapg2, and gap g3 is g1<g2<g3.

In the first exemplary embodiment, the cleaning unit 205 can expand andcontract in the arrow E direction which is vertical to the guide surface202 g of the upper conveyance guide 202. A height of the cleaning unit205 at the maximum compression is set to be smaller than the gap g1between guides, and the height of the cleaning unit 205 in an unloadedstate is set to be bigger than the gap g3 between guides.

As a result, even when the rail mechanism 201 bends by the weight of theconveyance unit 200 and the gap between the pair of the conveyanceguides 202 and 203 is changed, the cleaning unit 205 is constantly incontact with the guide surface 202 g of the upper conveyance guide 202when the cleaning unit 205 faces the guide surface 202 g of the upperconveyance guide 202. Therefore, the cleaning unit 205 can clean theguide surface 202 g of the upper conveyance guide 202 in the entirewidth direction.

FIG. 7 is bottom view for illustrating the upper conveyance guide 202and a cleaning unit 205 facing the upper conveyance guide 202.

As illustrated in FIG. 7, the cleaning unit 205 is provided outside of apaper passing area X in the upper conveyance guide 202. By arranging thecleaning unit 205 in this way, it becomes possible to clean an entirearea where the paper dust can adhere to the sheet, so that cleaning canbe efficiently carried out while saving a space. The arrow C in FIG. 7indicates a sheet conveyance direction.

Here, one end a1 and b1 of the sheet control members 204 and 204A (endson the back side) in the direction intersecting the sheet conveyancedirection, come to be in contact with the cleaning unit 205 when thelower conveyance guide 203 is drawn out from the printer main body 110.Another ends a2 and b2 of the sheet control members 204 and 204A (endson the front side) in the direction intersecting the sheet conveyancedirection, come to be in contact with the cleaning unit 205 when thelower conveyance guide 203 is attached to the printer main body 110.

Therefore, both ends a1 and a2 of the sheet control member 204, and endsof the ends b1 and b2 of the sheet control member 204A, which are incontact with the cleaning unit 205, are formed inclining with respect tothe sheet conveyance direction illustrated with the arrow C in FIG. 7.

Herewith, even when the side of the cleaning unit 205 comes to be incontact with the ends a1 and b1 of the sheet control members 204 and204A at a time of drawing out the conveyance unit 200 from the printermain body 110, the ends a1 and b1 of the sheet control members 204 and204A can be prevented from damage. In addition, even when the side ofthe cleaning unit 205 comes to be in contact with the ends a2 and b2 ofthe sheet control members 204 and 204A at a time of attaching theconveyance unit 200 to the printer main body 110, the ends a2 and b2 ofthe sheet control members 204 and 204A can be prevented from damage.

It is preferable that angles θ1, θ2, θ3, and θ4 of each of the ends a1,a2, b1, and b2 are inclined by 20° to 60° with respect to the sheetconveyance direction. Herewith, the ends a1, a2, b1, and b2 can beeffectively prevented from damage, and a life of the sheet controlmembers 204 and 204A can be prolonged.

FIG. 8 illustrates an attachment structure of the cleaning unit 205.

The cleaning unit 205 is provided detachably at the lower conveyanceguide 203. More specifically, the lower conveyance guide 203 has twoopenings 203 a and 203 b formed at the end on the back side, and thecleaning unit 205 has two projections 205 c and 205 d. The cleaning unit205 is fixed by inserting the projections 205 c and 205 d of thecleaning unit 205 into the openings 203 a and 203 b, and thrusting themto the attached members of the lower conveyance guide 203, which are notillustrated.

By taking the aforementioned configuration, the cleaning unit 205 can beeasily detached, and even when the cleaning unit 205 is consumable, timeand cost for exchange is low. Accordingly, entire cost including runningcost can be reduced.

Since the cleaning unit 205 can be attached and detached while theconveyance unit 200 (the lower conveyance guide 203) is drawn out, anoperation is easy, and a time taken for attaching and detaching thecleaning unit 205 can shorten, and a down time can be saved.

In the first exemplary embodiment, the cleaning unit 205 has the elasticmember 205 b as a pushing member. The second exemplary embodiment willbe described below, and a cleaning unit has a spring member as a pushingmember in the second exemplary embodiment.

FIG. 9 illustrates a configuration of a cleaning unit 205A in the secondexemplary embodiment. The cleaning unit 205A of the second exemplaryembodiment has a cleaning member 205 a similar to the cleaning member inthe first exemplary embodiment. The cleaning unit 205A has a metallicplate spring 205 b′ as a pushing member. The cleaning member 205 a isfixed on the plate spring 205 b′ with an adhesive. By using the platespring 205 b′ as the pushing member, the pushing member can have highdurability, and damaging and plastically deforming can be reduced.

In addition, in FIG. 9, a concave portion 203 c for collecting paperdusts is provided around the front side of the cleaning unit 205A (thefront side in the cleaning direction illustrated with the arrow A). Theconcave portion 203 c is formed outside the paper passing area of thelower conveyance guide 203. When the conveyance unit 200 (illustrated inFIG. 1) is drawn out, the cleaning unit 205A wipes paper dusts SWadhering to the guide surface of the upper conveyance guide 202(illustrated in FIG. 3) which has the sheet control members 204 and204A, and the paper dusts SW are collected in the concave portion 203 c.By forming the concave portion 203 c, the wiped paper dusts SW can beprevented from overflowing to the paper passing area of the lowerconveyance guide 203.

The first and second exemplary embodiments were described, but thepresent invention is not restricted in the first and second exemplaryembodiments.

The aforementioned exemplary embodiments use an electro-photographicimage forming apparatus as an example, in which the image forming unitforms a toner image as an image on a sheet, and the fixing unit fixesthe toner image. However, the present invention is not restricted tothis method. The present invention can be applied to image formingapparatuses such as those using an ink-jet method or offset printingmethod.

In the aforementioned exemplary embodiments, a number of the sheetcontrol members 204 and 204A is two. However, the number of a sheetcontrol member is not restricted to two, but can be one or three ormore. In addition, the present invention can be applied to an upperconveyance guide having no sheet control member.

In the aforementioned exemplary embodiments, the upper conveyance guide202 is fixed to the printer main body 110, and the lower conveyanceguide 203 is drawn out. However, the lower conveyance guide can be fixedto the printer main body, and the upper conveyance guide can be drawnout. In this case, the cleaning unit is provided at the upper conveyanceguide.

In the aforementioned exemplary embodiments, the present invention isapplied to a pair of the conveyance guides 202 and 203 between the skewcorrection mechanism 148 and the image forming unit 100. However, thepresent invention is not restricted to the pair, and can be applied toany other pair of conveyance guides.

Further, the cleaning member may be any material such as a brush ornonwoven fabric if the member can clean the guide surface.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2009-020827 filed Jan. 30, 2009, which is hereby incorporated byreference herein in its entirety.

1. A sheet conveying apparatus configured to convey a sheet along asheet conveyance path provided in an apparatus main body, the sheetconveying apparatus comprising: a first conveyance guide having a firstguide surface for guiding a sheet; a second conveyance guide having asecond guide surface arranged facing the first guide surface of thefirst conveyance guide, which serves as the sheet conveyance pathtogether with the first conveyance guide, and is drawable in a directionintersecting a sheet conveyance direction with respect to the apparatusmain body; and a cleaning unit provided on a back side in a drawing-outdirection of the second conveyance guide, and configured to clean thefirst guide surface of the first conveyance guide while moving togetherwith the second conveyance guide when the second conveyance guide isdrawn out from the apparatus main body, wherein the cleaning unitcomprises a cleaning member which is in contact with the first guidesurface of the first conveyance guide, a pushing member, which is anelastic member made of a foamable material, for pushing the cleaningmember toward the first guide surface, and a flexible member providedfacing a side surface on the back side of the elastic member in thedrawing-out direction of the second conveyance guide to protect theelastic member.
 2. The sheet conveying apparatus according to claim 1,wherein the cleaning member is formed by bundling a wire-shaped membermade of a synthetic resin, which is elastic and deformable.
 3. The sheetconveying apparatus according to claim 1, wherein the cleaning unit isprovided detachably at the second conveyance guide.
 4. A sheet conveyingapparatus configured to convey a sheet along a sheet conveyance pathprovided in an apparatus main body, the sheet conveying apparatuscomprising: a first conveyance guide having a first guide surface forguiding a sheet; a second conveyance guide having a second guide surfacearranged facing the first guide surface of the first conveyance guide,which serves as the sheet conveyance path together with the firstconveyance guide, and is drawable in a direction intersecting a sheetconveyance direction with respect to the apparatus main body; and acleaning unit provided on a back side in a drawing-out direction of thesecond conveyance guide, and configured to clean a first guide surfaceof the first conveyance guide while moving together with the secondconveyance guide when the second conveyance guide is drawn out from theapparatus main body, wherein the cleaning unit comprises a cleaningmember which is in contact with the first guide surface of the firstconveyance guide, and a spring member which pushes the cleaning membertoward the first guide surface.
 5. A sheet conveying apparatusconfigured to convey a sheet along a sheet conveyance path provided inan apparatus main body, the sheet conveying apparatus comprising: afirst conveyance guide having a first guide surface for guiding a sheet,the first conveyance guide comprises a guiding base body and a flexiblesheet control member, provided at the guiding base body, configured tocontact a sheet surface and to control an orientation of the sheet; asecond conveyance guide having a second guide surface arranged facingthe first guide surface of the first conveyance guide, which serves asthe sheet conveyance path together with the first conveyance guide, andis drawable in a direction intersecting a sheet conveyance directionwith respect to the apparatus main body; and a cleaning unit provided ona back side in a drawing-out direction of the second conveyance guide,and configured to clean a first guide surface of the first conveyanceguide while moving together with the second conveyance guide when thesecond conveyance guide is drawn out from the apparatus main body,wherein both ends of the flexible sheet control member in the directionintersecting the sheet conveyance direction are inclined with respect tothe sheet conveyance direction, wherein the cleaning unit comprises acleaning member which is in contact with the first guide surface of thefirst conveyance guide, and a pushing member for pushing the cleaningmember toward the first guide surface, the cleaning unit cleans theflexible sheet control member.
 6. An image forming apparatus comprisinga sheet conveying apparatus configured to convey a sheet along a sheetconveyance path provided in an apparatus main body, the image formingapparatus comprising: a first conveyance guide having a first guidesurface for guiding a sheet; a second conveyance guide having a secondguide surface arranged facing the first guide surface of the firstconveyance guide, which serves as the sheet conveyance path togetherwith the first conveyance guide, and is drawable in a directionintersecting the sheet conveyance direction with respect to theapparatus main body; and a cleaning unit provided on a back side in adrawing-out direction of the second conveyance guide, and configured toclean the first guide surface of the first conveyance guide while movingtogether with the second conveyance guide when drawing out the secondconveyance guide from the apparatus main body, wherein the cleaning unitcomprises a cleaning member which is in contact with the first guidesurface of the first conveyance guide, a pushing member, which is anelastic member made of a foamable material, for pushing the cleaningmember toward the first guide surface, and a flexible member providedfacing a side surface on the back side of the elastic member in thedrawing-out direction of the second conveyance guide to protect theelastic member.
 7. The image forming apparatus according to claim 6,wherein the cleaning member is formed by bundling a wire-shaped membermade of a synthetic resin which is elastic and deformable.
 8. The imageforming apparatus according to claim 6, wherein the pushing member is anelastic member made of a foamable material.
 9. The image formingapparatus according to claim 6, wherein the cleaning unit is provideddetachably at the second conveyance guide.
 10. An image formingapparatus configured to convey a sheet along a sheet conveyance pathprovided in an apparatus main body, the image forming apparatuscomprising: a first conveyance guide having a first guide surface forguiding a sheet; a second conveyance guide having a second guide surfacearranged facing the first guide surface of the first conveyance guide,which serves as the sheet conveyance path together with the firstconveyance guide, and is drawable in a direction intersecting a sheetconveyance direction with respect to the apparatus main body; and acleaning unit provided on a back side in a drawing-out direction of thesecond conveyance guide, and configured to clean a first guide surfaceof the first conveyance guide while moving together with the secondconveyance guide when the second conveyance guide is drawn out from theapparatus main body, wherein the cleaning unit comprises a cleaningmember which is in contact with the first guide surface of the firstconveyance guide, and a spring member which pushes the cleaning membertoward the first guide surface.
 11. An image forming apparatusconfigured to convey a sheet along a sheet conveyance path provided inan apparatus main body, the image forming apparatus comprising: a firstconveyance guide having a first guide surface for guiding a sheet, thefirst conveyance guide comprises a guiding base body and a flexiblesheet control member, provided at the guiding base body, configured tocontact a sheet surface and to control an orientation of the sheet; asecond conveyance guide having a second guide surface arranged facingthe first guide surface of the first conveyance guide, which serves asthe sheet conveyance path together with the first conveyance guide, andis drawable in a direction intersecting a sheet conveyance directionwith respect to the apparatus main body; and a cleaning unit provided ona back side in a drawing-out direction of the second conveyance guide,and configured to clean a first guide surface of the first conveyanceguide while moving together with the second conveyance guide when thesecond conveyance guide is drawn out from the apparatus main body,wherein both ends of the flexible sheet control member in the directionintersecting the sheet conveyance direction are inclined with respect tothe sheet conveyance direction, wherein the cleaning unit comprises acleaning member which is in contact with the first guide surface of thefirst conveyance guide, and a pushing member for pushing the cleaningmember toward the first guide surface, the cleaning unit cleans theflexible sheet control member.